Northern Flickers occur in two color forms: the "Red-shafted" in the West and the "Yellow-shafted" east of the Rocky Mountains. The Gilded Flicker, found in the Sonoran Desert of the Southwest, has recently been split off as its own species. The ice ages separated the ancestral flickers, keeping them scattered in several refugia for thousands of years. Today those barriers are gone. The Gilded has become adapted to the desert, whereas the two northern populations inhabit the same type of woodland habitat, with only the treeless Great Plains keeping them somewhat apart. All three forms interbreed where their ranges come together, and numerous confusing intermediates can be found. In the East, flickers are the only brown-backed woodpeckers, and the only woodpeckers in North America that commonly feed on the ground, searching for ants and beetle larvae.